cGAS Activation Accelerates the Progression of Autosomal Dominant Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: The renal immune infiltrate observed in autosomal polycystic kidney disease contributes to the evolution of the disease. Elucidating the cellular mechanisms underlying the inflammatory response could help devise new therapeutic strategies. Here, we provide evidence for a mechanistic link between the deficiency polycystin-1 and mitochondrial homeostasis and the activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of the interferon genes (STING) pathway. Our data identify cGAS as an important mediator of renal cystogenesis and suggest that its inhibition may be useful to slow down the disease progression. BACKGROUND: Immune cells significantly contribute to the progression of autosomal dominant polycystic kidney disease (ADPKD), the most common genetic disorder of the kidney caused by the dysregulation of the Pkd1 or Pkd2 genes. However, the mechanisms triggering the immune cells recruitment and activation are undefined. METHODS: Immortalized murine collecting duct cell lines were used to dissect the molecular mechanism of cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activation in the context of genotoxic stress induced by Pkd1 ablation. We used conditional Pkd1 and knockout cGas-/- genetic mouse models to confirm the role of cGAS/stimulator of the interferon genes (STING) pathway activation on the course of renal cystogenesis. RESULTS: We show that Pkd1 -deficient renal tubular cells express high levels of cGAS, the main cellular sensor of cytosolic nucleic acid and a potent stimulator of proinflammatory cytokines. Loss of Pkd1 directly affects cGAS expression and nuclear translocation, as well as activation of the cGAS/STING pathway, which is reversed by cGAS knockdown or functional pharmacological inhibition. These events are tightly linked to the loss of mitochondrial structure integrity and genotoxic stress caused by Pkd1 depletion because they can be reverted by the potent antioxidant mitoquinone or by the re-expression of the polycystin-1 carboxyl terminal tail. The genetic inactivation of cGAS in a rapidly progressing ADPKD mouse model significantly reduces cystogenesis and preserves normal organ function. CONCLUSIONS: Our findings indicate that the activation of the cGAS/STING pathway contributes to ADPKD cystogenesis through the control of the immune response associated with the loss of Pkd1 and suggest that targeting this pathway may slow disease progression.

Role of biophysics and mechanobiology in podocyte physiology.

Podocytes form the backbone of the glomerular filtration barrier and are exposed to various mechanical forces throughout the lifetime of an individual. The highly dynamic biomechanical environment of the glomerular capillaries greatly influences the cell biology of podocytes and their pathophysiology. Throughout the past two decades, a holistic picture of podocyte cell biology has emerged, highlighting mechanobiological signalling pathways, cytoskeletal dynamics and cellular adhesion as key determinants of biomechanical resilience in podocytes. This biomechanical resilience is essential for the physiological function of podocytes, including the formation and maintenance of the glomerular filtration barrier. Podocytes integrate diverse biomechanical stimuli from their environment and adapt their biophysical properties accordingly. However, perturbations in biomechanical cues or the underlying podocyte mechanobiology can lead to glomerular dysfunction with severe clinical consequences, including proteinuria and glomerulosclerosis. As our mechanistic understanding of podocyte mechanobiology and its role in the pathogenesis of glomerular disease increases, new targets for podocyte-specific therapeutics will emerge. Treating glomerular diseases by targeting podocyte mechanobiology might improve therapeutic precision and efficacy, with potential to reduce the burden of chronic kidney disease on individuals and health-care systems alike.

A high-throughput microfabricated platform for rapid quantification of metastatic potential.

Assays that measure morphology, proliferation, motility, deformability, and migration are used to study the invasiveness of cancer cells. However, native invasive potential of cells may be hidden from these contextual metrics because they depend on culture conditions. We created a micropatterned chip that mimics the native environmental conditions, quantifies the invasive potential of tumor cells, and improves our understanding of the malignancy signatures. Unlike conventional assays, which rely on indirect measurements of metastatic potential, our method uses three-dimensional microchannels to measure the basal native invasiveness without chemoattractants or microfluidics. No change in cell death or proliferation is observed on our chips. Using six cancer cell lines, we show that our system is more sensitive than other motility-based assays, measures of nuclear deformability, or cell morphometrics. In addition to quantifying metastatic potential, our platform can distinguish between motility and invasiveness, help study molecular mechanisms of invasion, and screen for targeted therapeutics.

Integrated multiomics implicates dysregulation of ECM and cell adhesion pathways as drivers of severe COVID-associated kidney injury.

COVID-19 has been a significant public health concern for the last four years; however, little is known about the mechanisms that lead to severe COVID-associated kidney injury. In this multicenter study, we combined quantitative deep urinary proteomics and machine learning to predict severe acute outcomes in hospitalized COVID-19 patients. Using a 10-fold cross-validated random forest algorithm, we identified a set of urinary proteins that demonstrated predictive power for both discovery and validation set with 87% and 79% accuracy, respectively. These predictive urinary biomarkers were recapitulated in non-COVID acute kidney injury revealing overlapping injury mechanisms. We further combined orthogonal multiomics datasets to understand the mechanisms that drive severe COVID-associated kidney injury. Functional overlap and network analysis of urinary proteomics, plasma proteomics and urine sediment single-cell RNA sequencing showed that extracellular matrix and autophagy-associated pathways were uniquely impacted in severe COVID-19. Differentially abundant proteins associated with these pathways exhibited high expression in cells in the juxtamedullary nephron, endothelial cells, and podocytes, indicating that these kidney cell types could be potential targets. Further, single-cell transcriptomic analysis of kidney organoids infected with SARS-CoV-2 revealed dysregulation of extracellular matrix organization in multiple nephron segments, recapitulating the clinically observed fibrotic response across multiomics datasets. Ligand-receptor interaction analysis of the podocyte and tubule organoid clusters showed significant reduction and loss of interaction between integrins and basement membrane receptors in the infected kidney organoids. Collectively, these data suggest that extracellular matrix degradation and adhesion-associated mechanisms could be a main driver of COVID-associated kidney injury and severe outcomes.